In each person resides a Heart Flower, which is connected to the great Heart Tree that watches over everyone. Protecting this tree are the Heartcatch PreCures, who defend it against the Desert Apostles, who plan to wilt everything and turn the world into a desert. However, when the current PreCure, Cure Moonlight, is defeated in battle and the Heart Tree loses its flowers, she sends two fairies, Chypre and Coffret, to the surface in order to seek out her replacement. They find Tsubomi Hanasaki, a shy flower-loving girl that had just moved into the city with her family. Joined by her new friend, Erika Kurumi, who becomes Cure Marine, she becomes Cure Blossom and fight against the Desert Apostles who transform the wilting Heart Flowers inside people into monsters known as Desertarians. By defeating these monsters, they gain Heart Seeds which allow the Heart Tree to become healthier again. As the story goes on, they are later joined by Itsuki Myoudouin, who becomes Cure Sunshine, and Yuri Tsukikage, who regains her powers as Cure Moonlight.